Alex Van Der Zwaan walks into the Washington field office of the FBI for processing before offering his plea at the Federal courthouse to making false statements to federal investigators, February 20, 2018.

A Dutch lawyer has admitted making false statements to US investigators examining links between Donald Trump’s election campaign team and Russia.

Alex van der Zwaan, 33, is the 19th person to be charged by special counsel Robert Mueller in the ongoing Trump-Russia investigation.

Van der Zwaan admitted in front of a US District Court in Washington, D.C. to having made false statements when questioned about his work for Ukraine’s Ministry of Justice.

A judge set his sentencing for April 3.

Van der Zwaan performed legal work for Paul Manafort and Rick Gates in Ukraine in 2012 while both worked for pro-Russian President Viktor Yanukovych. Manafort and Gates later became senior officials in Trump’s 2016 election campaign and have since been charged with conspiracy to launder money and failure to register as foreign agents in connection with their work for Yanukovych’s Kremlin-linked party in Ukraine.

Van der Zwaan represents the interests of numerous Russian oligarchs. He is also the son-in-law of German Khan, the Moscow-based billionaire oligarch who controls Russia’s Alfa Bank. The institution attracted scrutiny last year when a dossier published by former British spy Christopher Steele alleged that Alfa Bank had played a major role in meddling in the 2016 US election.

The court charged Van der Zwaanwith “willfully and knowingly making false, fictitious, and fraudulent statements and representations” to federal investigators about his work for the law firm Skadden, Arps and Affiliates in 2012.

He was also accused of misleading federal investigators about his communications with Gates, Manafort’s longtime associate who also worked on the Trump campaign during the 2016 election.

Skadden Arps was hired to draft a report that was used to justify former Ukrainian Prime Minister Yulia Tymoshenko‘s imprisonment on trumped-up charges. The man who commissioned the report for the Yanukovych regime by Manafort. Manafort serves as Trump’s campaign manager until he was fired in August 2016 amid revelations about extensive lobbying work for pro-Russian political parties.

Van der Zwaan’s guilty plea puts now more pressure on other former Trump aides to cooperate with Mueller as he looks into whether Russia tried to influence the election in favour of Trump by distributing disinformation amongst the campaign associates and through the use of online propaganda.

The lawyer’s case appears to underscore the extent of Mueller’s probe and of his interpretation of how far the investigation can go.

Manafort has, thus far, pleaded not guilty to Mueller’s charges.

A trial of Manafort and Gates is tentatively expected this autumn, though recent media reports have said that Gates is expected to plead guilty before the hearings begin.

Trump has called Mueller’s probe “a witch hunt” and Putin denies that his government conducted an operation to influence the US election.

Manafort and Gates worked as political consultants to Ukraine’s former pro-Russia president, Viktor Yanukovych, who was forced from office in 2014 after an uprising by the Ukrainian public turned into a deadly revolution.

The charging document unsealed on Tuesday concerned a report prepared at Manafort’s behest by attorneys at the prominent U.S. law firm Skadden Arps, Slate, Meagher and Flom. The attorneys included van der Zwaan. At the time the report was drawn, Manafort was close to Ukrainian and Russian political and business figures with ties to Russian President Vladimir Putin.

Andrew Weissmann, a prosecutor with Mueller’s office, told the court that Manafort and Gates funneled $4 million through offshore accounts to pay the law firm – which he did not identify by name – and Washington-based lobbying firms in connection with the report.